Have you thought about using the video card oven trick on it?
I didn't think of that but I'll definitely consider it.
Did you test your the TX650? There is a chance the PSU is failing intermittently or possibly just parts of the PSU.
Personally, I would test that PSU on another system/unit and also test the Cube with another PSU, preferably a verified working unit.
The PSU is now powering an Antminer S1 without issue so no problem there.